h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

As a signaller in WW2, Spike Milligan claims he was responsible for sending a false report of a German invasion fleet about to hit the beaches, which snowballed and put the whole of the Southern and Eastern coasts under invasion alert and mobilised the whole of the British armed forces (in modern-day terms, the cost of this false alarm would have gone into millions).

Milligan apparently misidentified a British convoy steaming into a nearby port. (But I wonder how well I'd have done, if with no training in telling our ships from theirs, I'd have been bunged into a sentry post on the coast, knowing an enemy was only thirty or so miles away and equipped to launch an invasion at any moment. Straining into the early-morning gloom and mist and seeing quite a lot of ships apparently steaming towards me, I might make an error of judgement too!)

While Spike Milligan claims he was responsible for setting the ball rolling, and the historical records tell us there was an invasion scare in September 1940 when the "red alert" codeword was wrongly transmitted, it might have to be seen in the context of the time: with the whole of the south coast on alert every day for signs of a German invasion thought to be imminent, and an awful lot of under-trained British soldiers manning an awful lot of sentry posts overlooking the Channel, I'm prepared to bet a lot of sentries misidentified things they saw... apparently Milligan sending the alarm should have been checked at a higher level befroe being forwarded (ie, one of his officers should have verified the sighting), but by a fluke in the system his radio signal bypassed his own regiment and went straight to the next level up.

The significance here is that this happened at Sentry Hill, Bexhill-on-Sea, which according to the German invasion plans, would have been RIGHT in the middle of the German invasion beaches...